Steel wool

Steel wool, also known as wire wool, is a bundle of strands of very fine soft steel filaments, used in finishing and repairing work to polish wood or metal objects, as well as for household cleaning.
Steel wool is made from low-carbon steel (low enough to be close to plain iron). It is not made by drawing "steel wool wire" through a tapered die, but rather by a process more like broaching where a heavy steel wire is pulled through a toothed die that removes a thin wire shaving.